Circuit breakers with thermal and magnetic tripping



July 28, 1959 C T. M. COLE 2,897,314

CIRCUIT BREAKERS WITH THERMAL AND MAGNETIC TRIPPING Filed June 11, 1956 ATTORNEY .ing tripping. is to improve circuit breakers of the type having pro- United States Patent CIRCUIT BREAKERS WITH THERMAL AND MAGNETIC TRIPPING Thomas M. Cole, Harrison, N.Y., assignor to Federal Pacific Electric Company, a corporation of Delaware Application June 11, 1956, Serial No. 590,712 20 Claims. (Cl. 200--88) The present invention relates to circuit breakers of the type having a current-responsive bimetal which trips the circuit breaker automatically upon occurrence of an overload. In more specific aspect, the invention relates to circuit breakers of the type havingthe current-responsive bimetal assembled to a moving contact member, as disclosed for example in Patent No. 2,681,396 filed jointly by Paul M. Christensen and myself, and assigned to the 'assignee of this application.

Circuit breakers of the type having a bimetal heated by overload currents for tripping the breaker have been known for long, as have magnetically tripped circuit breakers. In the thermally tripped form of circuit breaker, a bimetal is heated by the current passing through the circuit breaker and the heating causes the bimetal to deflect. When an overload is maintained long enough, the bimetal heats and deflects far enough to cause tripping. This desired delay allows for momentary moderate overloads. Where the magnetic field is reliedupon for tripping, a magnetic armature is utilized. Unless special delay means is included, magnetic response to Overload current is more immediate than thermal response.

Both forms of tripping have been combinedin circuit breakers, where thermal tripping is relied upon for responding to moderate overloads of comparatively long duration, and where magnetic tripping is relied upon for sudden overloads that exceed the thermal tripping level by a considerable margin.

An object of the present invention is to provide novel forms of combined thermal and magnetic circuit breakers, so called because of the means employed for caus- Afurther object of the present invention vision for thermal and magnetic tripping so as to com- .pensate partly or wholly for the efiects of the changing ambient temperatures on the current-responsive bimetal. In particular, an object of this invention is to provide a circuit breaker having integrated therein a thermal tripper, a sensitive magnetic tripper, and an ambient temperature compensator. A more specific but no less important object of the invention is to incorporate ambienttemperature compensation in abreaker having thermal and magnetic trippingdevices Where the circuitbreaker is of the type having a subassembly including a movable member bearing both a movable contact and the thermal tripping element.

Circuit breakers to which the present inventionis particularly applicable are of the small sizes ordinarily employed in domestic entrance equipment and in industrial distribution panelboards 'such as lighting panelboa-rds. Circuit breakers for these applications have been known for a great many years but only in recent years has the general public come to reap the benefit of these devices. The delay in the widespread use of early forms of this class of circuit breakers can be traced to high unit cost which in turn depends upon the diificulties of manufacturing the previously known forms .of circuit breakers.

Patented July 28, 1959 ice in this connection, an object of the present invention is to provide a novel circuit breaker construction adapted for large-scale low-cost production, incorporating the features of thermal and sensitive magnetic tripping and, advantageously, thermal compensation.

In the circuit breaker described in detail below, a latching assembly including thermal and magnetic trip means are provided. A latch pivoted on the current-responsive bimetal carries a compensating bimetal and a magnetic armature. This pivoted latch has a latching portion which holds the circuit breaker closed, when once closed, but is removed when tripping is to occur in response to either thermal deflection of the currentresponsive bimetal or in response to magnetic actuation of the armature-and-compensating bimetal latch. Magnetic tripping force is utilized efiiciently to overcome the latch friction in this novel circuit breaker, being in this respect far more sensitive for magnetic tripping than in circuit breakers where themagnetic field mustbend' the bimetal to trip the breaker...

The deflection of the current-responsive bimetal carries the pivoted element so that the face of the armature moves across the pole face of the electromagnet, thereby to maintain substantially constant magnetic air gap and substantially constant magnetic sensitivity. This deflection results both from changes in prevailing ambient temperature and from moderate currents (below tripping level) in the current-responsive bimetal.

The extent of latch engagement, i.e;, the distance tha the latch must move for tripping of the circuit breaker does not change appreciably'in'response to changes in ambient temperature because of the compensating bimetal carried by the pivoted assembly which in turn is carried by the current bimetalf "The compensating bimetal also achieves its purpose without appreciably affccting the air gap. i

The illustrative embodiment of the invention will be seen to include a current-responsive bimetal having shoulders thereon 'forminga pivot for a unit that carries both an armature and a compensating bimetal] This unit is pressed against the bimetal shoulders by the mechanismthat presses the 'contacts'"together. However, When the circuit 'breakeris open, and thereis no stress onthecompensating unit, this illu'strative circuit breaker will be seen to' embody uniqueifeatilres of construction for holding'the ipivotedunit in'it's assembled position and for-"biasing it in the reset direiction This construction includes'an element extending from thecurrent-responsive bimetal and providing an abutment for a compression spring which both biases the pivoted unit against the shoulders "on the currentfresponsive bimetal and which additionally biases the pivoted unit in thereset direction, opposite that of a magnetic tripping field. Thus, the spring retains the pivoted element in position and additionally provides pivoting bias in the direction to open the air gap between the armature and its activating electromagnet. l i

The nature of the invention and further details thereof will be apparent from the following description of the illustrative embodiment of the invention which is shown in the accompanying drawings. In those drawings:

Fig. 1 is a lateral view of a circuit breaker embodying theinvention, with a side cover removed to revealits mechanism and with the contacts of the circuit breaker closed against each other;

Fig. 2 is an enlarged det il of the latching mechanism of the circuit breaker in Fig. 1;

Fig. 3 is an endview of the mechanism inFig. 2;

Fig. 4is a fragmentary cross-section viewed from the Fig. 5 isa fragmentary cross-sectional view of the mechanism in Fig. 2, viewed from the line 55 therein; and

Fig. 6 is an enlarged detail of a portion of Fig. 2.

Referring now to the drawings, a circuit breaker having an enclosure 10 is seen to contain a first terminal 12 hearing a fixed contact 14 engaged in turn by moving contact 16 on moving contact arm 18. Compression spring 28 is biased to swing contact arm 18 counterclockwise about a pivot 22. This pivot is in the form of a cylindrical coil spring having its axis extending perpendicular to the view and having its ends in the bearings formed in the opposite walls of enclosure 10. Handle 24 which operates the contacts between closed position and open position, and reversely, has a portion 26 which locates the end of coil spring opposite the end of the spring that engages arm 18. Handle 24 additionally has an arm 28 to which a link 30 is pivoted, and this link has a pivoted connection to an actuator 32 pivoted to the end of contact arm 18 opposite that which carries the moving contact 16.

The handle is pivoted in the enclosure, as shown, and constitutes one element of a toggle, of which link 38 forms the other toggle element. This toggle drives actuator 32 clockwise when the handle is moved from open position (not shown) toward closed position, shown. Near the start of this stroke, the lower extremity 34 of the actuator engages a latching assembly 36, to be described below. Members 30 and 32 constitute a further toggle, both toggles being over-center but locked thus when latched. After the latching assembly arrests actuator extremity 34, the first toggle described drives moving contact arm 18 clockwise to close the contacts, coil spring 22 providing the resilience necessary to allow the toggle stroke to be completed despite arrest of contact 16 in engagement with fixed contact 14.

The latching assembly 36 includes a current-responsive bimetal 38 having its left-hand extremity fixed to contact arm 18 by an integral rivet 40 extending from the contact arm. A soft iron core 42 is also united by rivet 48 to contact arm 18 on the side of bimetal 38 which is remote from that contact arm. Accordingly, there is a direct conductive path established between bimetal 38 and contact arm 18.

A pair of shoulders 44 are formed on the lateral edges of bimetal 38 near the free or movable end thereof. Flat edges 46 at the bottom of lateral notches in a pivotally supported member 48 bear against these shoulders. There is a slight angle between the shoulders 44 and edges 46 so that, normally, there is engagement therebetween only at the upper edge of shoulder 44. Member 48 has a portion 50 which extends to the left and overlies bimetal 38 in the region of shoulders 44 and edges 46, and member 48 has a further portion 52 that engages bimetal 38 below shoulders 44. By means of this recessed formation, member 48 is rockably or pivotally carried on the shoulders 44 of bimetal 38. Tongue 56 on bimetal 38 is received and guided between the lateral portions 60 of member 48. A pair of inwardly directed bosses 54 extending from the two lateral portions or side Walls of member 48 act as stops, coacting with tongue 56, to limit the counterclockwise pivoting of member 48. The clockwise limit of pivoting is by engagement between the tongue 56 of bimetal 38 and the portion 58 of pivoted member 48 which interconnects the two lateral portions 60 thereof. These two lateral portions 60 of member 48 have in-turned portions 62 which form an abutment for compression coil spring 64. This spring is confined between these in-turned portions at the right-hand extremity of member 48 as viewed in the drawings and a swaged end 66 of an element 70' that extends from bimetal 38. This element is part of a length of wire forming the coil 72 about core 42 to constitute an electromagnet. The wire is joined at point '74 to the tongue 56, at the free or movable end of the current-responsive bimetal. Element 70 extends axially through coil spring 64 for fixing the transverse position for that coil spring, and for causing the spring to bias member 48 against shoulders '44; and the angle between the axis of the coil spring 64 and abutment 62 is slanted to bias member 48 counterclockwise about its pivot until arrested by stops 54.

Legs 60 are formed with a further pair of in-turned portions 76 which constitute an armature whose face is approximately parallel to the end of core 42. When bimetal 38 is heated, either by an increase in ambient temperature or by current flowing through the bimetal, the curving of the bimetal would only move armature 76 in its own place, approximately, so that there would be no significant change in the air gap between armature 76 and core 42.

Coil spring 64 is advantageously formed as a cylindrical helix, although it might broadly be formed as a conical coil spring or even as a leaf Spring confined be tween elements 62 and 66. In the configuration shown, the convolutions of the spring nearest portions 62 are canted or tilted so that the upper portion of the coil spring is in greater compression than the lower portion, and applies thrust along a line above shoulders 44. This spring, by endwise compression, maintains engagement of member 48 with shoulders 44 and the line of thrust of the spring provides counterclockwise bias for member 48, this bias acting to press stops 54 against tongue 56. This arrangement initially establishes the gap between core 42 and armature 76, and it Weakly resists tripping of the circuit breaker when a magnetic field is developed in electromagnet 42, 72.

An ambient temperature compensating bimetal 78 is united at its left-hand extremity to portion 58 of the pivoted member 48, and its right-hand extremity is formed with an abutment 80 which arrests the free end 34 of actuator 32. Element 78 is thus a latch that additionally provides ambient temperature compensation. This abut ment portion 80 is struck from the stock of the bimetal by having a lance 82 go part way across the bimetal with the end bent almost at right angles to provide a downward extending short length of bimetal joined integrally to the main horizontal length of bimetal 78. This downward extending portion forms a smooth surface with a sharp upper edge, minimizing face-to-face friction between portion 80 and actuator portion 34, and at the same time portion 80 presents a sharp edge that is important in defining a precise tripping edge.

Coil 72 which is joined by conductor 78 to the currentresponsive bimetal 38 at one extremity is joined at its opposite extremity to a length of flexible braid 84 which extends in turn to a fixed plug-in terminal 86 fixed in position by mating configurations in the insulating enclosure 10.

An electrical circuit may be traced from terminal 12 through contacts 14 and 16, moving contact arm 18, current-responsive bimetal 38, and coil 72, flexible braid 84, and plug-in terminal 86. In the event that a slow, steady, load current in the circuit protected by the circuit breaker should increase above the thermal tripping level, bimetal 38 shifts latch 4880 bodily downward. Bimetal 38 acts on bosses 54, to force ambient compensating bimetal 78 down and out of engagement with element 34. When this occurs spring 20 drives contact 16 away from fixed contact 14 and at the same time drives actuator 32 clockwise initially. Continuing action of the spring drives handle 24 clockwise andthis in turn reverses the rotation of actuator 32 so that it moves its latching end 34 to the right of the abutment extremity 80 of the latching mechanism.

In the event that the current through the circuit breaker should momentarily exceed the thermal tripping level by a large factor, such as by a factor of six or ten, as may be determined by design of the electromagnet,

' the magnetic field developed would promptly shift armature 76 and pivoted assembly 48,78 clockwise, thereby to release portion 34 of the circuit breaker linkage to cause automatic opening of the contacts under the impulse of spring 20.

Bimetal 38, in order to deflect downward in response to a rise of current, is arranged with its high expansion side upward, whereas compensating bimetal 78 is reversely arranged, with its low expansion side uppermost. In this way changes in ambient temperature result in portion 80 remaining virtually fixed and unchanging with ambient temperature changes. It has been noted that member 38 is comparatively thick and stifi, and this is in order to resist the stresses imposed thereon by the circuit breaker mechanism. Compensating bimetal 78, being substantially shorter, is of thinner stock yet provides the same necessary minimum resistance to mechanical column-like stresses, and is stiff enough to overcome the friction between latch portions 34 and 80 when tripping is to occur, either thermally or magnetically.

The pivot of member 32 on arm 18 embodies insulation, to prevent a current path being formed from bimetal 38 through bimetal 78 and actuator 32. Such parallel path from weld point 74 through actuator 32 to contact arm 18 would tend to provide a current path of uncertain resistance paralleling the current path through bimetal 3S; and in the event of severe overload, arcing might develop at latching portions 34, 80 which would cause undesired roughness to develop at the latch- Iing surfaces.

A further current path might develop, which is undesirable, between core 42 and armature 76, in the event that the armature should actually contact the pole face. "This current path would develop, and current would flow,

Z bec-ause of the volt drop that would be developed from end to end of current-responsive bimetal 38. Upon short circuit it may be equal to the rated voltage of the circuit breaker. To prevent this from occurring either core 42 or armature 78 or both may be coated with insulation; and similarly coil 72 is insulated, advantageously of enameled wire.

The foregoing detailed description of an exemplary embodiment-of my invention includes novel features that are naturally susceptible of modification and varied application by those skilled in the art without departing from the invention, and therefore the invention should be broadly construed in accordance with its full spirit 'and scope.

I claim:

1. A circuit breaker having a pair of contacts and operating means therefor including a handleoperable to open and close the contacts, a spring-biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means normally cooperating with and restraining said releasable member and effective to disengage and release said releasable member in response to overloads, said release means including a current-responsive bimetal having a portion that deflects in response to current, a pivot and a pivoted latch thereon normally engaging and arresting said releasable member and operatively connected to said bimetal for disengaging and releasing said releasable member in response to overload, said latch havinga recessed formation open at one side and having confining portions on the other three sides for receiving said pivot, and a spring having one end thereof arranged to act against the latch so as .to bias the latch both pivotally toward said normal position restraining'said releasable member and in the direction to maintain assembly of the latch on its pivot.

2. A circuit breaker having a pair ofv contacts and operating means therefor including a handle operable to open and close the contacts, a spring-biased releasable member effective when released to cause trip-free open- ;ingof the contacts, .andautomatic releasemeans for .said releasable member, saidrelease means including a pivot, a pivoted latch thereon having a normal position engaging and obstructing said releasable member and another position disengaging said releasable member, said latch having a recessed formation receiving said pivot, said formation being open at the side thereof opposite the point of engagement of the latch with the releasable member, and a spring having one end thereof biasing the latch both toward said normal position and into engagement with said pivot, said release means including a current-responsive bimetal operatively connected to said latch and effective to disengage said latch from said releasable member.

3. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means normally cooperating with and restraining said releasable member and effective to disengage and release said releasable member in response to overloads, said release means including a pivot, a pivoted latch thereon having a normal position in the path of said releasable member and engaged thereby and operable out of engagement therewith, said latch having a recess formation receiving said pivot, said formation being open at the side thereof opposite the point of engagement of the latch with the releasable member, and a spring having one end thereof arranged to act against the latch so as to bias the latch both toward said normal position and into engagement with said pivot, said release means including an electromagnet operatively related to said latch. I

,4. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to ,open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a pivot, a pivoted latch thereon having a normal position in the path of said releasable member and engaged therebyand operableout of engagement therewith, said latchhavingarecess formation receiving said pivot, said formation being open at the side thereof opposite the point of engagement of the latch with the releasable member, and a spring having one end thereof arranged to act against said latchso as to bias the latch both toward said normal position and into engagement with said pivot, said release means including a currentresponsive bimetal and an electromagnet operatively con nected to said latch.

5. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close thecontacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal having a shouldered portion at the endthereof which defiectsin response to current variations and a unitary latch engaged by said releasable member ,when in a normal position and operable out of such engagement. to free the releasable member and said latch having a recessed formation opening in one direction forreceiving said shouldered portion of the bimetal so as to be rockably supported thereon, said spring biased releasable member being disposedto press said latch against said shouldered portion when the circuit breaker is closed, and spring mea ns,biasing said unitary latch toward said shouldered portion for maintaining assembly therewith at times when the latch is not pressed by the releasable member, said spring bias means being also operative to bias the latch toward said normal position.

6. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal having a shouldered portion at the end thereof which deflects in response to current variations and a unitary latch engaged by said releasable member when in a normal position and operable out of such engagement to free the releasable member and said latch having a recessed formation opening in one direction for receiving said shouldered portion of the bimetal so as to be rockably supported thereon, said spring biased releasable member being disposed to press said latch against said shouldered portion when the circuit breaker is closed, and an electromagnet operatively related to said latch and responsive to sudden current overloads of higher level than that required for thermal tripping by bimetal deflection.

7. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal having a shouldered portion at the end thereof which deflects in response to current variations and a unitary latch engaged by said releasable member when in a normal position and operable out of such engagement to free the releasable member and said latch having a recessed formation opening in one direction for receiving said shouldered portion of the bimetal so as to be rockably supported thereon, said spring biased releasable member being disposed to press said latch against said shouldered portion when the circuit breaker is closed, and a spring having one end thereof biasing said unitary latch both toward said shouldered portion for maintaining assembly therewith at times when the latch is not pressed by the releasable member, and biasing the latch toward said normal position, and a current-responsive electromagnet operative to rock said latch in the direction to release the releasable member.

8. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal having a shouldered portion at the end thereof which deflects in response to current variations and a latch having a recessed formation opening in one direction for receiving said shouldered portion of the bimetal so as to be rockably supported thereon, said spring biased releasable member being disposed to press said latch against said shouldered portion when the circuit breaker is closed and said latch is in a normal position engaging and obstructing said releasable member and said latch being operable out of such engagement to release the releasable member, an element on said current-responsive bimetal extending beyond said shouldered portion as a unitary part of the bimetal, and a compression spring having one end acting against said extending element and having its other end reacting against said latch to bias the latch against said shouldered portion at times when the latch is not pressed by the releasable member, said other end of said spring also being disposed to bias the latch toward said normal position.

9. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a member having a shouldered portion, and a latch having a recessed formation opening in one direction for receiving said shouldered portion so as to be rockably supported thereon, said spring biased releasable member being disposed to press said latch against said shouldered portion when the circuit breaker is closed and when said latch is in normal position obstructing said releasable member, an element extending beyond said shouldered portion as a unitary part of the bimetal, and a compression spring having the respective ends thereof confined between said extending element and said latch to bias the latch against said shouldered portion at times when the latch is not pressed by the releasable member, said spring also being disposed to bias the latch toward said normal position.

10. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal having a shouldered portion at the end thereof which deflects in response to current variations and a latch engageable with and disengageable from said releasable member and having a recessed formation opening in one direction for receiving said shouldered portion of the bimetal so as to be rockably supported thereon, said spring biased releasable member being disposed to press said latch against said shouldered portion when the circuit breaker is closed and when said latch is in normal position obstructing said releasable member, an element constituting a unitary extension of said current-responsive bimetal beyond said shouldered portion, and a compression spring confined between said element and said latch to bias the latch against said shouldered portion at times when the latch is not pressed by the releasable member, said spring also being disposed to bias the latch toward said normal position, said latch bearing an armature, an electromagnet supported adjacent said armature and effective when sufliciently energized to rock the latch and thereby release said releasable member.

11. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal, a latch supported thereon by a separable connection, said releasable member normally engaging and pressing the latch in a direction to prevent separation of the separable connection and said latch being operable by said bimetal out of engagement with said releasable member, and a spring having one end thereof acting against and biasing said latch in the direction to resist separation of the separable connection and also biasing the latch toward a position in which it obstructs said releasable member.

12. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a pivotal support, a latch supported thereon by a separable connection, said latch engaging and obstructing said releasable member when the circuit breaker is closed, said latch being operable out of engagement with said releasable member, and said releasable member pressing the latch in a direction to prevent separation of the separable connection, and current-responsive means including a bimetal and an electromagnet operative to remove said latch from its position obstructing said releasable member.

13. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member elfective when released to cause trip-free opening of the contacts, release" means including a pivotal support, a latchsnpported thereon by a separable connection, said latch normally engaging and obstructing said releasable member when the circuit breaker is closed and said latch being operable out of engagement with said releasable member, and said releasable member pressing. the latch in a direction to prevent separation of the separable connection, and a current-responsive means ineluding a bimetal and an electromagnet operative to remove said latch from its position obstructing said releasable member, and said latch carrying an ambient temperature-responsive bimetal.

14. A circuit breaker having a pair of contacts and operating means therefor including a handle opening to open and close the contacts, a spring biased releasable member eifective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal, a latch supported thereon by a separable connection and normally in engagement with said releasable member but operable out of engagement therewith, said releasable member pressing the latch in a direction to prevent separation of the separable connection when the circuit breaker is closed, coacting stop means on said latch and said bimetal for limiting pivoting of the latch in reset direction, whereby the deflection of the current-responsive bimetal in the releasing direction bodily shifts said latch, a spring engaging both the latch and means carried by the bimetal and biasing said latch in the direction to resist separation of the separable connection and also biasing the latch to- Ward coaction of said stop means, and an electromagnet adjacent said current-responsive bimetal and coacting with a magnetic armature on said latch to operate said latch in the release direction and to separate said coacting stop means.

15. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member eifective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal, a latch supported thereon by a separable connection, said releasable member pressing the latch in a direction to prevent separation of the separable connection, coacting stop means on said latch and said bimetal for limiting pivoting of the latch in reset direction, whereby the deflection of the currentresponsive bimetal in the releasing direction bodily shifts said latch, a spring engaging the latch and biasing said latch in the direction to resist separation of the separable connection and also biasing the latch toward coaction of said stop means, and an electromagnet adjacent said current-responsive bimetal and coacting with a magnetic armature on said latch to operate said latch in the release direction and to separate said coacting stop means, and an ambient temperature responsive bimetal having one end fixed to said latch as a part thereof, said compensating bimetal extending generally in the same direction as said current-responsive bimetal and extending into coaction with said releasable member.

16. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal, a latch supported thereon by a separable connection and normally in engagement with said releasable member but operable out of engagement therewith, said releasable member pressing the latch in a direction to prevent separation of the separable connection when the circuit breaker is closed and when said latch is in its normal position obstructing said releasable member, and a spring engaging both the latch means carried by the bimetal and biasing said latch in the di-' rection to resist separation of theseparable connection and also biasing the latch toward said normal position, said bimetal and said latch having inter-engaging stop means coacting with said spring to establish said normal position, said separable connection and said stop means being effective to shift the latch bodily in the direction to release the releasable member in response to current increases, and said electromagnet being eifective to rock said latch in the release direction.

17. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal having a fixed end and an end movable laterally in response to current variations, said movable end having a pair of shoulders at the lateral edges thereof and a projecting portion between said shoulders, a rockable member having notched lateral portions engaging said shoulders and flanking said projecting portion of the bimetal and having an interconnecting portion between said lateral portions, an ambient temperature compensating bimetal carried by said interconnecting portion and extending to latching engagement with said releasable member when the circuit breaker is closed and biased thereby in the direction to press said rockable member against said shoulders, said rockable member and said projecting bimetal portion having interengaging stop portions limiting relative rocking thereof, a projecting element on said current-responsive bimetal between said lateral portions, and a compression coil spring acting between said projecting element and said rockable member, said coil spring being arranged to act both to push the rockable member against said shoulders and to bias said rockable member pivotally about said shoulders in the direction for latching engagement with said releasable member.

18. A circuit breaker having a pair of contacts and operating means therefor including a handle operable to open and close the contacts, a spring biased releasable member eifective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a support having a pair of shoulders at the lateral edges thereof and a projecting portion between said shoulders, 21 rockable latch adapted to obstruct said releasable member and having notched lateral portions engaging said shoulders and flanking said projecting portion, said rockable member and said projecting portion having interengaging stop portions limiting relative rocking thereof, a projecting element on said support between said lateral portions, and a compression coil spring acting between said projecting element and said rockable member, said coil spring being arranged to act both to push the rockable member against said shoulders and to bias said rockable member pivotally about said shoulders in the direction for latching engagement with said releasable member.

19. A circuit breaker having a pair of separable contacts and operating means therefor including a springbiased movable contact arm carrying one of said contacts, a releasable member carried by said contact arm and effective to hold the contact arm in elosed-contact position, and automatic release means for said releasable member carried bodily by said contact arm, said release means including a pivotal support, a latch supported thereby by a separable connection, said latch obstructing said releasable member When the circuit breaker is closed and said releasable member pressing the latch in a direction to prevent separation of the separable connection, and current-responsive means including a bimetal and an electromagnet operative to remove said latch from its position obstructing said releasable member.

20. A circuit breaker having a pair of contacts and 11 operating means therefor including a handle operable to open and close the contacts, a spring-biased releasable member effective when released to cause trip-free opening of the contacts, and automatic release means for said releasable member, said release means including a current-responsive bimetal having a shouldered portion at the movable end thereof, a rockable latch member having a notched formation receiving said shouldered portion, an electromagnet adjacent said current responsive bimetal including an armature on said rockable member and a wire coil joined to said current-responsive bimetal, the wire of the coil extending therebeyond, and a compression spring acting between said rockable member and a deformation on said extending wire to bias the rockable latch member against said shouldered portion and in the latching direction.

References Cited in the of this natent UNITED STATES PATENTS Hulbert Mar. 1, 1955,. 

